PH Flux

Has anyone had this problem or know the answer. I am doing dwc with maxi bloom ec is about 2.0 I added hydroguard to my bucket 60ml 3 weeks ago. Each day I have to check my ph because it continues to rise at approxamitly 1 pm each day when I check my ph it is between 6.3and 6.5 I want to keep it at 6 so I add ph down I get it to 6 and the next afternoon it is back up to 6.3 or so. I have never had a ph fluxuation like this any ideas

keep changing it. thats small dialy maintance once you get the hang, i got about the same problem.

Thanks I dont mind ajusting it but I was wondering if there was a problem. I feel better knowing its just a freak thing When I mix a new batch of maxi grow it has a ph of about 5.3 so I dont ajust it and when I add the fert it helps